RELATED
to the honeybee, but comparatively more hardier, the bumblebee has
adapted well to live and survive in the cooler parts of the world,
including the Himalayas. The queen honeybee's job is to only lay eggs
but if it wants to start a new colony, it needs a swarm of workers,
whereas the queen bumblebee does it all alone.

In spring, when the
temperature rises, the snow melts and the flowers bloom, the queen
bumblebee sets out in search of a suitable place to start a new colony.
Since she has to build her own brood cell, lay eggs and sit on them in
much the same manner as a bird to hatch her first brood of workers
solely by herself, an intricate dwelling structure is out of question.
Her nest has to be readymade, and is usually built in the abandoned hole
of a vole or fieldmouse, or in a grass tussock.

After the suitable
abandoned nest-hole is found, the queen refurbishes it according to its
requirements, lining it with moss and grass. Once the interior is done,
she constructs a cup from the wax secreted from her abdomen and after
filling it with pollen lays about a dozen fertilised eggs in it and
seals it with wax. Fertilised eggs produce female workers. After this,
the queen builds and stocks a honey container in the nest.

After sometime, the eggs
hatch into larvae and the mother feed them on pollen and honey that she
pushes through a hole in the cup. Soon larvae pupate and after about 20
days come out as adult female worker bees. Meanwhile, the queen keeps on
constructing cups and repeating the whole process, but soon a time comes
when the colony becomes little larger and the queen starts devoting more
and more time to egg-laying. The number of bees grows very fast and by
the end of summer, the nest-hole is filled with several hundred
offspring, produced by one and the same female. This is the time when
the queen mother lays two special batches of eggs, one of which will
produce drones and the other queens. The new bumblebee queens and males
leave the nest and fly off to mate and, in the females' case, to find
new colonies after hibernating. Of the total number of newborns, only
the young, fertilised queens survive to start new colonies in the
following spring.

Like many other bees and wasps, bumblebees too are able to reproduce without
actually fertilising their eggs. Reproductive females in these insects mate in
summer or autumn, and the sperms received are stored in receptacles inside their
bodies. The most interesting part is that bumblebees mate only once but the
supply of sperms lasts their entire lives - which can be up to little more than
a year. During her entire lifetime, the queen exercises total control over her
store of sperms and decides whether or when to use them for the purpose of
fertilising eggs as they pass through her reproductive system. Each egg is
fertilised with one sperm, but if she withholds them the unfertilised eggs
produce males.

Belonging to the order of bees and
wasps, Hymenoptera, bumblebees are easily recognised by predators, as they too
are able to inflict a painful sting like their relatives. Usually people believe
that bees and wasps bite if handled, which is not true. Instead it is their
sting, a modified ovipositor (egg-laying structure) placed at the end of the
body that causes pain when injected. This also makes it clear that only females
can cause pain.

Whenever this weapon with a venom
sac attached to it is used, it usually remains stuck in the wound, causing a
shooting pain and swelling to the victim and the bee dies. It is the
non-producing worker bee that stings and lays down her life in the defence of
the colony.

As has been already mentioned,
these insects live in a cold environment. Naturally, the question arises as to
how these tiny creatures survive such harsh conditions? Bumblebees are among
those animals that demonstrate substantial variations in body temperature
between different parts of their bodies, a phenomenon called regional
heterothermy.

Since these insects are smaller in
size, they have large surface-to-volume ratios, which plays a major role in
losing body heat rapidly. The flight muscles of these insects also operate
properly only at temperatures between 30 degrees and 40 degrees C. In such
conditions it is very important to keep the body warm to survive, so the
bumblebees, like many beetles and moths, have evolved a mechanism for conserving
in their thoraxes (part of the body between neck and the abdomen) much of the
heat produced by muscles as they go through very rapid contraction cycles, with
the result that the thoraxes are much warmer than the rest of their bodies. With
this system arises another problem of heat being lost through diffusion and
convection to other colder parts of the body.

To counter this problem insects
have evolved some more mechanisms, which helps them in solving the problem to a
large extent. For one, they have modified cuticular scales on their outer
thoracic surfaces that resemble their fur and, secondly, they have the ability
to control the pattern of blood flow in their bodies so as to restrict heat
transfer from the thorax to other body parts.